The spread component (SC) is numerically equal to the theoretical forward speed of the headfire in feet/minute. It is the most variable of the fire danger indices, with variations being caused by changes in wind speed and in moisture content of the live and dead fuels. SC is another index produced by the Oklahoma Fire Danger Model. Wind speed, slope and fine fuel moisture are key inputs in the calculation of the spread component, thus accounting for a high variability from day-to-day.
Spread component is a function of the fuel model being used, the live and dead fuel moistures, and the weather conditions. If the fuel types and loads are substantially different than those in the fuel model being used, there will be inaccuracies.
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